I didn't think you'd be at home but I just called by on the off chance.

我想你不会在家，只是碰碰运气顺路来看一下。

《牛津词典》

She scanned the crowd on the off chance of seeing someone she knew.

她扫视着人群，抱着一线希望看是否有熟人。

《牛津词典》

I called in at the office on the off chance that you would still be there.

我打电话给办公室，想看看你是否可能还在那里。

《牛津词典》

This was it. What could be an impossible effort in the history of spaceflight was ready to lift off on its final chance for success.

VOA: special.2009.07.01

On the off chance you were going to get them the same thing for Hanukkah or Christmas, just get them something else instead.

FORBES: No More Impulse Buys: How To Teach Your Kids About Money

Why do I habitually pop into random liquor stores to see if, on the off chance, they have my favorite rare bottle collecting dust somewhere?

WSJ: Rye Whiskey: Do the Rye Thing | Half Full

For now, the House GOP leadership seems to have no way to gracefully end the probe, and may be inclined to keep it going on the off chance it strikes gold.

CNN: By Jackie Koszczuk and Dan Carney, CQ Staff Writers